ENVIRONMENTAL STIMULI INFLUENCE ESTROGEN-DEPENDENT COURTSHIP TRANSITIONS AND BRAIN AROMATASE-ACTIVITY IN MALE RING DOVES

In paired ring doves, Streptopelia risoria, male and female reproducti ve behaviour undergoes a series of synchronised transitions. The durat ion of each phase depends on the reproductive development of the pair. This study examines the effect of the environment in which behaviour is shown on both oestrogen-dependent courtship transitions and formati on of oestrogen in the brain. The structuring of the cage environment had an immediate effect on transitions in male courtship behaviour. Ma les which were tested with females in a cage environment with a perch and a nest bowl (complex cage) displayed significantly less aggressive courtship and more nest-orientated behaviour than males tested with f emales in a cage environment without perch or nest bowl (simple cage). The response of males, which showed aggressive and nest-orientated co urtship behaviour, to reproductively advanced females (abdominal lengt h 1.4-1.6 cm) about to lay eggs or females in earlier stages of reprod uctive development (abdominal length 0.8-1.1 cm) did not differ initia lly. On the eighth day of 15-min daily tests, there was, however, an i ncrease in aggressive courtship to females with smaller abdomens. This result suggests that male aggressiveness is more likely when the male and female reproductive cycles are not synchronised. We also tested w hether environmental factors and the male's hormonal condition, which affect male courtship interactions, influence the formation of behavio urally effective oestrogen by aromatisation of testosterone in the bra in. The aromatase activity was measured in;he preoptic and anterior hy pothalamic areas in relation to the time spent in interaction with fem ales each day. Both intact and castrated males which interacted interm ittently (15 min each day for 9 days) had higher preoptic aromatase ac tivity than males which interacted continuously with females. The mate s which had high brain aromatase activity and had interacted intermitt ently with females were considered to represent the initial stages of the cycle. We conclude that cage environment and female reproductive c ondition influence the course of courtship interactions. Oestrogen for mation in the male brain is affected by the type of interaction.